<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>

<body>
    <script>
        function fn(x, y) {
            if (!x || !y) {
                // throw 会阻断代码执行
                // throw '你没有传参'
                throw new Error('少了参数')
            }
            return x + y
        }
        // console.log(fn()) // NaN
        console.log(fn(1, 2))
        console.log(fn(1))
    </script>
</body>

</html>